1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus.
2. Description of Related Art
In general, an electrophotographic image forming apparatus (such as a printer, a copy machine, and a fax machine) is configured to irradiate (expose) a uniformly-charged photoconductor (for example, a photoconductor drum) with (to) laser light based on image data to form an electrostatic latent image on the surface of the photoconductor. The electrostatic latent image is then visualized by supplying toner from a developing device to the photoconductor on which the electrostatic latent image is formed, whereby a toner image is formed. Further, the toner image is directly or indirectly transferred to a sheet through an intermediate transfer belt, followed by heating and pressurization for fixing, whereby an image is formed on the sheet.
When a jam is caused in the above-described image forming apparatus, sheet advancing is manually performed to pull out the sheet from the apparatus, thereby eliminating the jam. In addition, in an image forming apparatus in which a conveyance section that inverts a sheet for duplex printing is provided as a sheet conveyance unit (so-called Auto-Duplex Unit (ADU)), when a jam is caused in the sheet conveyance unit, the user can pull out the sheet conveyance unit from the image forming apparatus to remove the sheet remaining in the sheet feeding path. Various members (for example, a guide member) provided on the sheet feeding path can be exposed by pulling out the sheet conveyance unit from the image forming apparatus, and thus a sheet can be carefully removed from an suitable place so as not to scatter unfixed toner.
In addition, a technique for unjamming has been proposed in which a sheet is cut and divided into a part on which a toner image is transferred and a part on which no toner image is transferred, and the former part is removed from the sheet ejecting side whereas the latter part is removed from the sheet feeding side, thereby preventing unfixed toner from being attached on a registration roller (for example, Japanese Patent Application Laid-Open No. 10-20593).
A jam which is caused during image formation on flat sheets can be relatively readily eliminated in the above-described way. However, to eliminate a jam which is caused during an image formation on a long sheet such as a roll sheet and a continuous sheet, the long sheet has to be cut with a cutter or the like on the outside of the apparatus and has to be pulled out from the apparatus by performing sheet advancing, which is a complicated and unsafe task. In addition, when an end portion of a cut long sheet falls to the floor, dust adheres to the long sheet, and consequently the interior parts of the apparatus may possibly be contaminated or damaged when the long sheet is again conveyed. Furthermore, since the long sheet has to be externally fed to the image forming apparatus for conveyance, sheet conveyance takes time.
In addition, a long sheet is typically exists over the entire length of the sheet feeding path (the state where the sheet protrudes from the sheet conveyance unit to the sheet feeding side or the sheet ejecting side), and when the sheet conveyance unit is pulled out at the time of unjamming, the sheet may be torn and broken, and paper debris may remain in the apparatus. Such paper debris remaining in the apparatus may damage components of the apparatus.
The term “long sheet” as used herein means a sheet having a sheet length greater than that of flat sheets (for example, A3-sheets) which can be contained in a commonly used sheet-feed tray section provided in an image forming apparatus, and the term “long sheet” includes, for example, roll sheets, continuous sheets, flat sheets for banner or hanging banner, and the like.